Biological samples, for example histology samples, may be examined in histopathological examination by light microscopy using bright-field illumination. Molecular pathology is the examination, at a molecular level, of biomolecules associated with disease. From a histopathological examination, important information about patient diagnosis, prognosis, and treatment options can be elucidated. Pathologists study the histopathologic architecture, tissue morphology, and/or signals associated with the detection of particular biomolecules (e.g. nucleic acid or proteins). A number of assays presently available detect and/or quantify proteins (i.e. immunohistochemistry (IHC)), nucleic acids (i.e. in situ hybridization (ISH)), carbohydrates (i.e. histochemistry (HC)), and enzymes (i.e. enzyme histochemistry (EHC)).
Histopathological examination of pigment-containing samples is difficult because pigments can obscure the evaluation of the samples. For example, excessive amounts of melanin pigments hamper histopathological assessments of melanocytic lesions by obscuring cellular morphology, obscuring chromogenic staining, and hindering antibody-antigen interactions.